The Measurement and Analysis of Maximal Expiratory Flow Volume Loops at Low Lung Volumes in Children With Cystic Fibrosis and Normal Routine Lung Function.

The current study is based on current investigators previously published patho-physiologic and lung CT studies in small airways intrinsic obstruction, emphysema, and asthma. Current investigators have demonstrated that despite the presence of normal routine spirometry including normal FEV1(L), FVC (L), and FEV1/FVC% that unsuspected small airways obstruction, and emphysema can be detected. This has been achieved by presence of isolated abnormal expiratory airflow limitation at low lung volumes on the maximal expiratory flow volume curves. This includes abnormal expiratory airflow at 75% and 80% expired lung volume. Current investigators believe investigators will be able to detect unsuspected small airways intrinsic obstruction, and peripheral airway bronchiectasis proven by lung CT, in patients with cystic fibrosis despite presence of pre bronchodilator normal routine spirometry.